Electron microscopic evaluation of two-bundle anatomically reconstructed anterior cruciate ligament graft

Growth-related changes in the ultrastructure of the quadriceps tendon

BACKGROUND

The purpose of this study was to investigate the effect of growth on the ultrastructural characteristics of the quadriceps tendon (QT).

METHODS

Eighteen included patients were classified into three groups based on age and epiphyseal plate condition: the 'immature group' consisted of patients with open epiphyseal plates (11.5 ± 1.6 years old; mean ± standard deviation), the 'young group' consisted of patients aged <20 years with closed epiphyseal plates (15.8 ± 1.0 years), and the 'adult group' consisted of all patients aged >20 years (29.8 ± 11.3 years) irrespective of epiphyseal plate condition. Tendon tissue samples were used for ultrastructural analysis by transmission electron microscopy. Minimum collagen fibril diameters were measured from the cross sections of collagen fibril images using Image J software. The average number of collagen fibers per sample was 797 ± 109, and the average collagen fibril diameter of each sample was compared using one-way analysis of variance.

RESULTS

The mean collagen fibril diameter was 89.7 ± 14.4 nm in the immature group, 94.8 ± 16.4 nm in the young group, and 107.2 ± 12.1 nm in the adult group, with significant differences between the immature and adult groups, and between the young and adult groups (P = 0.001 and P = 0.021, respectively); however, no significant differences were observed between the immature and young adult groups (P = 0.49).

CONCLUSIONS

The collagen fibril diameter of the QT was found to have increased with growth. The study provided insights into graft selection.

Graft Intra-Articular Remodeling and Bone Incorporation in ACL Reconstruction: The State of the Art and Clinical Implications

The knee is one of the most frequently affected joints in sports trauma, and anterior cruciate ligament (ACL) injury and meniscal tears are the most common lesions. ACL reconstruction (ACLR) remains the treatment of choice for patients willing to return to their previous activity. There are different surgical techniques and different possible usable grafts. The graft used for ACLR surgery undergoes a bone incorporation process and an intra-articular remodelling named ligamentization until it reaches characteristics similar to the native ligament. After the first incorporation stage, the remodelling process is divided into an early stage that could last 4 weeks, a proliferative stage that lasts 4 to 12 weeks, and a final stage of ligamentization that could last over 1 year. The period of return to sport (RTS) after ACLR, which is becoming shorter and shorter, can be a high-risk period for athletes due to the risk of graft failure. This systematic review aims to define the phases of the ligamentization process considering graft type and fixation techniques, as well as the graft's anatomopathological and biomechanical characteristics, to evaluate a criterion-based rehab progression and maximize patient outcomes for an RTS respecting graft biology. The rehabilitative program has to promote and optimize the graft remodelling and incorporation processes; moreover, it has to accommodate physiological graft healing and avoid overloading. An early RTS and noncompliance with the biological characteristics of the graft in the various phases are associated with a high incidence of re-injury.

Differences in cellular and microstructural properties of the semitendinosus muscle tendon between young and adult patients

BACKGROUND

Poor outcomes associated with anterior cruciate ligament reconstruction in paediatric patients are a major concern. The tendon structure and its cellular characteristics are key factors that affect the mechanical properties of tendons. This study aimed to evaluate the effects of growth on the cellular and microstructural properties of the tendon of the semitendinosus muscle in humans.

METHODS

Semitendinosus muscle tendon samples from 76 patients who underwent ligament reconstruction were examined and divided into three groups: immature (10.8 ± 2.7 years old), young (16.5 ± 1.8 years old), and adult (35.2 ± 8.6 years old), based on age and the state of the epiphyseal plate in the distal femur. The number of tendon cells per unit area was assessed, and the major-to-minor-length ratio of the tendon cell nuclei was calculated to evaluate the shape of the nuclei using haematoxylin and eosin staining. The collagen fibril diameter and distribution were determined using electron microscopy.

RESULTS

The major-to-minor-length ratio of the tendon cell nuclei significantly increased with age (p-value; immature vs. young: 0.018, young vs adult: 0.001, immature vs adult: 0.001). The shape of the tendon cell nuclei was rounder in the immature group and more elongated in the adult group. A significant decrease in the number of tendon cells was observed with age (immature: 565 ± 134/mm², young: 356 ± 105/mm², adult: 272 ± 81/mm²; p-value: immature vs young: 0.001, young vs adult: 0.012, immature vs adult: 0.001). The mean fibril diameter in the immature group was significantly smaller (p-value: immature vs young: 0.018, young vs adult: 0.001, immature vs adult: 0.001). The distribution of the collagen fibrils changed from right skewed in the immature group to flat in the adult group.

CONCLUSIONS

The characteristics of the tendon cells and the microstructure of collagen in muscle tendons significantly changed with age.

A Simplified Double-Bundle Anterior Cruciate Ligament Reconstruction by the Three-Inside Technique With Two Suspension Buttons and One Interference Screw

In comparison with the single-bundle technique, double-bundle anterior cruciate ligament (ACL) reconstruction has proven its superiority regarding biomechanical studies and clinical outcomes in both rotational knee stability and anterior translation function. However, the complexity and risk of complications remain a great concern for the orthopaedic surgeon performing double-bundle ACL reconstruction. We present a simplified double-bundle ACL reconstruction by the 3-inside technique with 2 suspension buttons and 1 interference screw. The semitendinosus tendon is tripled to be the anteromedial (AM) bundle, whereas the gracilis is doubled for the posterolateral (PL) bundle. We perform a 3-socket approach with an inside-out femoral tunnel for the AM bundle, an outside-in femoral tunnel for the PL bundle, and a retrograde tibial socket for the tibial bundle. Thus, this technique is, simply, a combination of 2 procedures: one single all-inside method (for the AM bundle) and one outside-in method (for the PL bundle), with which most arthroscopic surgeons are familiar. The AM and PL bundles are fixed at 30° and 45°, respectively, using 2 suspension buttons and 1 interference screw. Our simplified technique could reduce surgical costs and minimize complications while maintaining isometric position and appropriate graft size for each patient.

Assessment of Graft Maturity After Anterior Cruciate Ligament Reconstruction Using Autografts: A Systematic Review of Biopsy and Magnetic Resonance Imaging studies

Purpose

The purpose of this investigation was to evaluate systematically the literature concerning biopsy, MRI signal to noise quotient (SNQ) and clinical outcomes in graft-maturity assessment after autograft anterior cruciate ligament reconstruction (ACLR) and their possible relationships.

Methods

The systematic review was reported and conducted according to the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines. Studies through May 2019 evaluating methods of intra-articular ACL autograft maturity assessment were considered for inclusion. Eligible methods were histologic studies of biopsy specimens and conventional MRI studies reporting serial SNQ and/or correlation with clinical parameters.

Results

Ten biopsy studies and 13 imaging studies, with a total of 706 patients, met the inclusion criteria. Biopsy studies show that graft remodeling undergoes an early healing phase, a phase of remodeling or proliferation and a ligamentization phase as an ongoing process even 1 year after surgery. Imaging studies showed an initial increase in SNQ, peaking at approximately 6 months, followed by a gradual decrease over time. There is no evident correlation between graft SNQ and knee stability outcome scores at the short- and long-term follow-up after ACLR.

Conclusions

The remodeling of the graft is an ongoing process even 1 year after ACLR, based on human biopsy studies. MRI SNQ peaked at approximately 6 months, followed by a gradual decrease over time. Heterogeneity of the MRI methods and technical restrictions used in the current literature limit prediction of graft maturity and clinical and functional outcome measures by means of MRI graft SNQ after ACLR.

Level of evidence

Level IV, systematic review, including level III and IV studies.

[A correlation study between the Mohawk expression level and the collagen fiber diameter of hamstring tendon graft after anterior cruciate ligament reconstruction]

Objective

To evaluate the correlation between the Mohawk (MKX) expression level and the collagen fiber diameter of autologous hamstring tendon graft during the stable graft remodeling phase after anterior cruciate ligament (ACL) reconstruction.

Methods

Between January 2018 and August 2018, patients who underwent arth-roscopic single-bundle anatomical ACL reconstruction with autologous hamstring tendons for at least 48 months and also underwent second-look arthroscopy were enrolled in study. During the second-look arthroscopic procedures, ACL graft biopsies were performed from the surface of central part of the ligament. MKX expressions of ACL grafts were analysed by real-time fluorescent quantitative PCR (qRT-PCR). The ultrastructure of collagen fibers of grafts were evaluated by transmission electron microscopy, which included average diameter of collagen fibers (D _c), average diameter of large-diameter collagen fibers (D _L), average diameter of small-diameter collagen fibers (D _S), and large-small collagen fibers ratio (R _L/S). The correlation between MKX expression level and graft collagen fiber diameter was calculated.

Results

Twenty-six patients met the selection criteria and their ACL graft specimens were enrolled in the study. The interval between ACL reconstruction and second-look arthroscopy was 52-128 months, with an average of 78.6 months. Arthroscopic graft remodeling score was 3-6 (mean, 4.8). There were 17 cases of excellent remodeling and 9 cases of fair remodeling. All ACL grafts showed typical bimodal distributions of both large-diameter collagen fibers and small-diameter collagen fibers, but the ultrastructural characteristics of the graft collagen fibers were different according to different remodeling status under arthroscopy. The D _C, D _L, D _S, and R _L/S of the graft specimens were (65.2±9.3) nm, (91.6±10.5) nm, (45.7±8.6) nm, and 0.73±0.12, respectively. The relative expression level of MKX was 1.42±0.11, which was positively linearly correlated with D _C, D _L, and R _L/S, and the correlation coefficient was statistically significant ( r=0.809, P=0.000; r=0.861, P=0.000; r=0.942, P=0.000), while there was no significant correlation between D _S and relative expression level of MKX ( r=0.147, P=0.238). Regression analysis showed that the relative expression level of MKX could predict the D _C, D _L, and R _L/S results of the ACL graft specimens ( P<0.05).

Conclusion

After autologous hamstring tendon grafts stepped into stabilized remodeling phase, MKX expression level could predict the diameter measurement results of collagen fibers and be used as an important evaluation basis for graft collagen anabolic metabolism.

[Histological properties of autogenous hamstring grafts after anterior cruciate ligament reconstruction]

Objective

To investigate the histological characteristics of autogenous hamstring grafts after anterior cruciate ligament (ACL) reconstruction.

Methods

The patients who underwent arthroscopic single-bundle ACL reconstruction with autogenous hamstring tendons and were followed up at least 4 years and also underwent second-look arthroscopy between March 2017 and December 2017 and met the selection criteria were considered for enrollment. Graft quality under arthroscopy was evaluated as good remodeling group (GRG, the total scores were 4-6) and poor remodeling group (PRG, the total scores were 1-3) according to synovial and vascular coverage, the apparent tension of the grafts, the thickness and retear of the grafts. During the second-look arthroscopic procedures, ACL graft biopsies were performed. Normal ACL tissues harvested from the patients under 60 years old who underwent total knee arthroplasty were designated as normal controls. Graft vascularity, cellular morphology, cellular metabolism, and collagen fibril distribution were analyzed.

Results

The 18 specimens (11 cases of GRG group and 7 cases of PRG group) and 9 native ACL biopsied tissue sample were enrolled into the study. Arthroscopy scores were 2-6 (mean, 4.7). The biology under light microscopy of GRG group was similar to that of native ACL in control group. There was no significant difference in the scores of graft vascularity and cellular morphology between GRG group and control group ( P>0.05), while PRG group was significantly lower than the other two groups ( P<0.05). Transmission electron microscope evaluation showed that GRG group and control group had better collagen fibril distribution and lower levels of cellular metabolism than PRG group ( P<0.05). There was no significant difference in cellular metabolism between GRG and control groups ( P>0.05), while collagen fibril distribution score of GRG group was significantly lower than that of control group ( P<0.05).

Conclusion

While good remodeling grafts under arthroscopy in histological maturation period was proved to be more similar to normal ACL on ultrastructure properties under light and electron microscope, ultra structural differences regarding collagen fibril distribution still persist.

Ligamentization of Autogenous Hamstring Grafts After Anterior Cruciate Ligament Reconstruction: Midterm Versus Long-term Results

BACKGROUND

In previous studies, unimodal, small-diameter collagen fibrils have been commonly observed as the final collagen ultrastructure of the implanted grafts used in anterior cruciate ligament (ACL) reconstruction. However, the native ACL and hamstring tendon show bimodal collagen fibril distribution, consisting of both large- and small-diameter collagen fibrils.

HYPOTHESIS

Bimodal collagen fibril distribution of the graft is a common phenomenon after ACL reconstruction with hamstring tendon grafts and is time dependent.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 52 patients who underwent double-bundle ACL reconstruction using autogenous hamstring tendons and who also underwent second-look arthroscopic surgery were enrolled. The patients were divided into 2 groups according to the time interval between the 2 operations: the midterm group (27 patients), with a 13- to 30-month time interval between operations, and the long-term group (25 patients) with a 31- to 62-month interval. During the second-look arthroscopic procedures, ACL graft biopsies were performed. Normal ACL tissues were harvested from 9 patients who underwent total knee replacement, and biopsy specimens of the to-be-grafted semitendinosus tendon tissues were also harvested from another 9 patients who underwent ACL reconstruction with hamstring tendons, which were designated as normal controls. Graft vascularity, cellularity, metaplasia, cellular metabolism, and collagen fibril distribution were analyzed.

RESULTS

Large-diameter (>100 nm) collagen fibrils were detected in 81.5% of the specimens in the midterm group and in 68.0% of the specimens in the long-term group. A typical bimodal distribution mode was observed in 62.6% of the specimens in the midterm group and in 52.0% of the specimens in the long-term group. There was no significant difference between groups with respect to the presence of large-diameter collagen fibrils, bimodal distribution, graft vascularity, cellularity, metaplasia, or cellular metabolic status.

CONCLUSION

Graft ultrastructural maturation, characterized by large-diameter collagen fibrils and a bimodal collagen fibril distribution, is a common phenomenon and is not time dependent in the midterm to long term.

CLINICAL RELEVANCE

After hamstring tendon ACL reconstruction, the implanted grafts can transform into ACL-like tissue with a similar ultrastructure and metabolism, implying their usefulness as grafts.

PRP Augmentation for ACL Reconstruction

Current research is investigating new methods to enhance tissue healing to speed up recovery time and decrease the risk of failure in Anterior Cruciate Ligament (ACL) reconstructive surgery. Biological augmentation is one of the most exploited strategies, in particular the application of Platelet Rich Plasma (PRP). Aim of the present paper is to systematically review all the preclinical and clinical papers dealing with the application of PRP as a biological enhancer during ACL reconstructive surgery. Thirty-two studies were included in the present review. The analysis of the preclinical evidence revealed that PRP was able to improve the healing potential of the tendinous graft both in terms of histological and biomechanical performance. Looking at the available clinical evidence, results were not univocal. PRP administration proved to be a safe procedure and there were some evidences that it could favor the donor site healing in case of ACL reconstruction with patellar tendon graft and positively contribute to graft maturation over time, whereas the majority of the papers did not show beneficial effects in terms of bony tunnels/graft area integration. Furthermore, PRP augmentation did not provide superior functional results at short term evaluation.

Double-bundle versus single-bundle reconstruction for anterior cruciate ligament rupture in adults

BACKGROUND

Arthroscopic reconstruction for anterior cruciate ligament rupture is a common orthopaedic procedure. One area of controversy is whether the method of double-bundle reconstruction, which represents the 'more anatomical' approach, gives improved outcomes compared with the more traditional single-bundle reconstruction.

OBJECTIVES

To assess the effects of double-bundle versus single-bundle for anterior cruciate ligament reconstruction in adults with anterior cruciate ligament deficiency.

SEARCH METHODS

We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (to February 2012), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 2), MEDLINE (1966 to February week 3 2012) and EMBASE (1980 to 2012 Week 8). We also searched trial registers, conference proceedings, and contacted authors where necessary.

SELECTION CRITERIA

Randomised and quasi-randomised controlled clinical trials comparing double-bundle versus single-bundle reconstruction for anterior cruciate ligament (ACL) rupture in adults.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected articles, assessed risk of bias and extracted data. We contacted investigators to obtain missing information. Where appropriate, results of comparable studies were pooled.

MAIN RESULTS

Seventeen trials were included. These involved 1433 people, mostly young physically active adults. All included trials had methodological weaknesses and were at risk of bias, notably selection bias from inadequate or lack of allocation concealment. Data for pooling individual outcomes were available for a maximum of nine trials and 54% of participants.There were no statistically or clinically significant differences between double-bundle and single-bundle reconstruction in the subjective functional knee scores (subjective IKDC score, Tegner activity score, Lysholm score) in the intermediate (six months up to two years since surgery) or long term (two to five years from surgery). For example, the long term results for the Lysholm score (0 to 100: best score) were: mean difference (MD) 0.12, 95% confidence interval (CI) -1.50 to 1.75; 5 trials, 263 participants). The only trial reporting on long term knee pain found no statistically significant differences between the two groups. There were no significant differences between the two groups in adverse effects and complications (e.g. infection reported by nine trials (7/285 versus 7/393; risk ratio (RR) 1.14, 95% CI 0.46 to 2.81); graft failure reported by six trials (1/169 versus 4/185; RR 0.45; 95% CI 0.07 to 2.90).Limited data from five trials found a better return to pre-injury level of activity after double-bundle reconstruction (147/162 versus 208/255; RR 1.15, 95% CI 1.07 to 1.25). At long term follow-up, there were statistically significant differences in favour of double-bundle reconstruction for IKDC knee examination (normal or nearly normal categories: 325/344 versus 386/429; RR 1.05, 95% CI 1.01 to 1.08; 9 trials), knee stability measured with KT-1000 arthrometer (MD -0.74 mm, 95% CI -1.10 to -0.37; 5 trials, 363 participants) and rotational knee stability tested by the pivot-shift test (normal or nearly normal categories: 293/298 versus 382/415; RR 1.06, 95% CI 1.02 to 1.09; 9 trials). There were also statistically significant differences in favour of double-bundle reconstruction for newly occurring meniscal injury (9/240 versus 24/358; RR 0.46, 95% CI 0.23 to 0.92; 6 trials) and traumatic ACL rupture (1/120 versus 8/149; RR 0.17, 95% CI 0.03 to 0.96; 3 trials). There were no statistically significant differences found between the two groups in range of motion (flexion and extension) deficits.

AUTHORS' CONCLUSIONS

There is insufficient evidence to determine the relative effectiveness of double-bundle and single-bundle reconstruction for anterior cruciate ligament rupture in adults, although there is limited evidence that double-bundle ACL reconstruction has some superior results in objective measurements of knee stability and protection against repeat ACL rupture or a new meniscal injury. High quality, large and appropriately reported randomised controlled trials of double-bundle versus single-bundle reconstruction for anterior cruciate ligament rupture in adults appear justified.

ANATOMICAL RECONSTRUCTION OF ANTERIOR CRUCIATE LIGAMENT OF THE KNEE: DOUBLE BAND OR SINGLE BAND?

OBJECTIVE

To evaluate the double-band and single-band techniques for anatomical reconstruction of the anterior cruciate ligament of the knee and demonstrate that the double-band technique not only provides greater anterior stability but also causes less pain and a better subjective patient response.

METHODS

We selected 42 patients who underwent anterior cruciate ligament reconstruction, by means of either the single-band anatomical reconstruction technique, using flexor tendon grafts with two tunnels, or the double-band anatomical reconstruction technique, using four tunnels and grafts from the semitendinosus and gracilis tendons. All fixations were performed using interference screws. There was no variation in the sample. Before the operation, the objective and subjective IKDC scores, Lysholm score and length of time with the injury were evaluated. All these variables were reassessed six months later, and the KT-1000 correlation with the contralateral knee was also evaluated.

RESULTS

There was no significant difference between the two groups in subjective evaluations, but the single-band group showed better results in relation to range of motion and objective evaluations including KT-1000 (with statistical significance).

CONCLUSION

Our study demonstrated that there was no difference between the two groups in subjective evaluations, but better results were found using the single-band anatomical technique, in relation to objective evaluations.

Prospective evaluation of patients with anterior cruciate ligament reconstruction using a patient-based health-related survey: comparison of single-bundle and anatomical double-bundle techniques

PURPOSE

To compare the treatment outcomes of single-bundle and anatomical double-bundle anterior cruciate ligament (ACL) reconstructions, we used the patient-based health-related QOL questionnaire SF-36 to evaluate patients with ACL injury who underwent surgical reconstruction using the two techniques.

PATIENTS AND METHODS

A prospective study was performed on patients who were diagnosed with ACL injury and underwent ACL reconstruction. Eighty-four male patients who were followed for at least 2 years were analyzed in this study. Forty-four patients were operated by single-bundle technique, and 40 by double-bundle technique. SF-36, Lysholm score, anterior tibial translation, and pivot shift were assessed before surgery and 6, 12 and 24 months after surgery.

RESULTS

In the preoperative SF-36 survey, the scores of almost all the subscales were lower than the national standard scores in both groups. After operation, the scores of all the subscales improved to the national standard values in all patients, but no difference was observed between two groups. Lysholm score, distance of anterior tibial translation and pivot shift positive rate improved significantly after operation in all patients, but there were no significant differences between two groups.

DISCUSSION

Although good clinical results have been reported for double-bundle ACL reconstruction, some studies reported no clear difference compared to the conventional single-bundle technique. In the present study, significant improvements were achieved after operation in both groups, confirming the usefulness of both techniques. No clear merit of one method over the other was found, not only from the conventional objective assessments but also from the patient-based subjective evaluation.

The "ligamentization" process in anterior cruciate ligament reconstruction: what happens to the human graft? A systematic review of the literature

BACKGROUND

Surgical anterior cruciate ligament reconstruction using tendon grafts has become the standard to treat the functionally unstable anterior cruciate ligament-deficient knee. Although tendons clearly differ biologically from ligaments, multiple animal studies have shown that the implanted tendons indeed seem to remodel into a ligamentous "anterior cruciate ligament-like" structure.

PURPOSE

The goal of this study was to systematically review the current literature on the "ligamentization" process in human anterior cruciate ligament reconstruction.

STUDY DESIGN

Systematic review.

METHODS

A computerized search using relevant search terms was performed in the PubMed, MEDLINE, EMBASE, and Cochrane Library databases, as well as a manual search of reference lists. Searches were limited to studies examining the healing of the intra-articular portion of the tendon graft based on biopsies of this graft obtained from a living human.

RESULTS

Four studies were determined to be appropriate for systematic review, none of them reaching a level of evidence higher than 3. All reports considered autografts. Biopsy specimens were evaluated by light or electron microscopy and analyzed for vascularization, cellular aspects, and appearance of extracellular matrix. All authors universally agreed that the tendon grafts survive in the intra-articular environment. Based on changes observed in the healing grafts with regard to vascularization, cellular aspects, and properties of the extracellular matrix, different chronologic stages in the ligamentization process were discerned.

CONCLUSION

The key finding of this systematic review is that a free tendon graft replacing a ruptured human anterior cruciate ligament undergoes a series of biologic processes termed "ligamentization." The graft seems to remain viable at any time during this course. Histologically, the mature grafts may resemble the normal human anterior cruciate ligament, but ultrastructural differences regarding collagen fibril distribution do persist. Different stages of the ligamentization process are described, but no agreement exists on their time frame. Problematic direct transmission of animal data to the human situation, the limited number of reports considering the ligamentization process in humans, and the potential biopsy sampling error attributable to superficial graft biopsies necessitate further human studies on anterior cruciate ligament graft ligamentization.

The effect of platelet concentrates on graft maturation and graft-bone interface healing in anterior cruciate ligament reconstruction in human patients: a systematic review of controlled trials

PURPOSE

To systematically review the current evidence for the effects of platelet concentrates on (1) graft maturation and (2) graft-bone interface healing in anterior cruciate ligament (ACL) reconstruction in human, controlled trials and for ensuing differences in clinical outcomes.

METHODS

A systematic search of PubMed, CINAHL (Cumulative Index to Nursing and Allied Health Literature), Embase, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews was performed for controlled trials of human ACL reconstruction with and without platelet concentrates. Data validity was assessed, and data were collected on graft maturation, graft-bone interface healing, and clinical outcome.

RESULTS

Eight studies met the inclusion criteria. Seven studies reported on graft maturation with significantly better outcomes in the platelet groups in 4, and there were large differences in means in an additional 2 studies. Five studies reported on tunnel healing, and 4 found no difference between groups. Three studies assessed clinical outcome but found no differences, regardless of whether they had shown a beneficial effect (1 of 3) or no effect (2 of 3) of platelets on graft and tunnel healing.

CONCLUSIONS

The current best evidence suggests that the addition of platelet concentrates to ACL reconstruction may have a beneficial effect on graft maturation and could improve it by 20% to 30% on average, but with substantial variability. The most likely mode of action is that treatment with platelets accelerates graft repopulation and remodeling, and this interpretation is supported by the existing data and is biologically plausible. However, the current evidence also shows only a very limited influence of platelet concentrates on graft-bone interface healing and no significant difference in clinical outcomes.

LEVEL OF EVIDENCE

Level III, systematic review of Level I, II, and III studies.

"Anatomic" anterior cruciate ligament reconstruction: a systematic review of surgical techniques and reporting of surgical data

PURPOSE

The aim of this systematic review was to evaluate studies published on anatomic double-bundle anterior cruciate ligament (ACL) reconstruction.

METHODS

A systematic electronic search was performed by use of the Medline and Embase databases. Studies that were published from January 1995 to April 2009 were included. The selection criteria were studies that reported on a surgical technique for "anatomic double-bundle ACL reconstruction" on skeletally mature living human subjects and were written in English. Data collected and analyzed included a variety of surgical data. Tables were created to provide an overview of surgical techniques for anatomic ACL reconstruction.

RESULTS

Seventy-four studies were included in this review. Some surgical factors were adequately reported in the majority of the articles: visualizing the native ACL insertion sites, placing the tunnels in the footprint, graft type, and fixation method. However; ACL insertion site measurement, femoral intercondylar notch measurement, individualization of surgery, and intraoperative/postoperative imaging were poorly reported. The most variety was seen in knee flexion angle during femoral tunnel drilling and tensioning pattern of the grafts.

CONCLUSIONS

For most surgical data, there was a gross under-reporting of specific operative technique data. We believe that the details of an "anatomic" operative technique are crucial for the valid interpretations of the outcomes. Thus we encourage authors to report their surgical technique in a specific and standardized fashion.

Electron microscopy of the remodelling process in hamstring tendon used as ACL graft

The purpose of the present study was to make a histological analysis of the remodelling process of hamstring tendon graft used as Anterior Cruciate Ligament (ACL). The hamstring graft of eight patients was biopsied at different follow-up times from 1 to 10 years. The specimens were analysed with transmission electron microscopy (TEM) at ultrastructural level comparing them with a native ACL and a native hamstring graft. The hamstring graft was found to undergo ultrastructural changes in terms of number and diameter of fibrils with the major changes occurring in the first 2 years. At longer times after surgery (48 and 120 months) no important further changes were evident and the ultrastructure did not vary substantially from 2 to 10 years. In conclusion, the hamstring tendon used as ACL graft undergoes a transformation process but does not match the ultrastructure pattern of a normal ACL up to 10 years.

Translational studies in anterior cruciate ligament repair

Translational research, which can be explained as the principle of combining advances in both basic research and clinical understanding in a bedside-to-bench-to-bedside approach, has become one of the central themes of present-day medical research. One orthopedic problem that has strongly benefited from such an approach is tissue-engineering-enhanced primary repair of the anterior cruciate ligament. Recent years have shown a clearer definition of the clinical problem and established an underlying mechanistic cause of the incapacity of the anterior cruciate ligament to heal-the premature loss of provisional scaffold in the wound site. These clinical findings were then translated into a research objective, namely, to replace the missing scaffold with a biomaterial with appropriate structural and bio-stimulatory characteristics. Subsequently, a tissue-engineering-based treatment using a collagen-platelet composite was developed and tested in vitro. After proofing the efficacy of this new treatment in the laboratory, it was translated into a potential clinical application, which showed highly successful results in structural integrity and biomechanical capacity in large animal testing. This approach of defining the scientific mechanism underlying a clinical observation and then using that information to design new therapies is but one example of how translational research in tissue engineering can help define and develop new treatments for challenging problems faced by patients.

Graft healing in anterior cruciate ligament reconstruction

Graft healing within the bone tunnel after anterior cruciate ligament (ACL) reconstruction is still a complex, poorly understood biological process that is influenced by multiple surgical and postoperative variables. However, remarkable advances in knowledge of this process have been made based primarly on animal models. According to the findings of this review, some surgical and postoperative variables are known to directly affect time-course and quality of graft-tunnel healing. The type of graft, graft motion, and fixation methods have shown to directly affect time-course and quality of graft-tunnel healing. Therefore, the application of early and aggressive rehabilitation protocols should be cautious when using soft-tissue graft, allografts, and direct or aperture type of fixation for ACL reconstruction. With regard to graft placement, several cadaveric models showed biomechanical advantages of a more anatomical graft location; however, there are no studies that explore the relationship between graft placement and healing process. The precise effect of graft tensioning, graft/tunnel diameter disparity, and graft length within the bone tunnel in the graft healing process remains unclear and requires more research. To enhance graft-tunnel healing, tissue-engineering approaches, including the use of growth factors, mesenchymal stem cells, and periosteum graft augmentation, have been tested on animal models. These have shown promising results in terms of enhancement of bone-graft healing rate.

Graft remodeling and ligamentization after cruciate ligament reconstruction

After reconstruction of the cruciate ligaments, replacement grafts have to undergo several phases of healing in the intra-articular graft region and at the site of graft-to-bone incorporation. The changes in the biological and mechanical properties of the healing graft in its intra-articular region are described as the ligamentization process. Significant knowledge has been added in the understanding of the several processes during the course of graft healing and is summarized in this article. The understanding of the spatial and time-dependent changes as well as the differences between the different models of graft healing are of significant importance to develop strategies of improved treatment options in cruciate ligament surgery, so that full restoration of function and mechanical strength of the intact cruciate ligaments will be achieved.

A prospective randomized study of 4-strand semitendinosus tendon anterior cruciate ligament reconstruction comparing single-bundle and double-bundle techniques

PURPOSE

A randomized clinical study was conducted to compare the outcome between double-bundle (DB) and single-bundle (SB) anterior cruciate ligament (ACL) reconstructions with 4-strand semitendinosus tendon (ST).

METHODS

We divided 68 patients with unilateral ACL injury into 2 groups according to their birth date, and they were followed up in person for a mean of 25 months (range, 18 to 41 months). Each group of 34 patients underwent either DB or SB ACL reconstruction using 4-strand ST with EndoButton femoral fixation (Smith & Nephew Endoscopy, Andover, MA) and anchor staple tibial fixation. There was no difference between the 2 groups with regard to age at surgery, sex, follow-up period, period before surgery, combined meniscus injuries, and athletic activity level. All patients followed the same postoperative program. They were evaluated using manual knee laxity tests, instrumented anterior laxity measurements (KT-1000 arthrometer [MEDmetric, San Diego, CA]), knee extension and flexion strength testing, and so on. General knee condition was evaluated by use of the Lysholm knee score and subjective rating scale.

RESULTS

There were no significant differences between the 2 groups with regard to range of motion, thigh girth, muscle strength, and Lysholm score. Manual knee laxity testing revealed that negative Lachman and pivot-shift test results were found in more patients in the DB group than in the SB group. KT measurements averaged 2.4 mm in the SB group and 1.4 mm in the DB group, which was statistically significantly different. Statistical analysis showed no significant difference regarding all of the modified International Knee Documentation Committee-categorized data between the 2 groups.

CONCLUSIONS

This randomized controlled trial indicated that DB ACL reconstruction via 4-strand ST is superior to the SB technique with regard to anterior and rotational stability; however, it fails to show any subjective difference.

LEVEL OF EVIDENCE

Level I, prospective randomized controlled clinical study.

Neoligamentization process of BTPB used for ACL graft: histological evaluation from 6 months to 10 years

Following anterior cruciate ligament (ACL) reconstruction with the middle third part patellar tendon, the graft undergoes histological rearrangement due to biomechanical action, which transforms it into a structure similar to the normal ACL. The purpose of our study was to make a qualitative and quantitative histological evaluation, by transmission electron microscopy (TEM), of the neoligamentization process of a bone-patellar tendon-bone (BTPB) graft used as pro-ACL at different follow-up times. We analysed the ultrastructure of collagen fibrils by focusing on their size and distribution with respect to a normal patellar tendon and a normal ACL used as controls. Our results showed that up to 24 months follow-up, progressive ultrastructural changes towards the normal ACL were observed. At longer times after surgery (48 and 120 months) no further changes were evident and the ultrastructure showed a marked reduction in large fibrils, which was typical of the control patellar tendon, and a significant increase in small fibrils. The ultrastructure seemed to combine fibrils from two different morphological units. The BPTB graft used as ACL underwent a transformation process for up to two years. After that period the transformation ceased and for ten years failed to reach the ultrastructural aspect of a normal ACL. However, from an architectural point of view the graft was slowly transformed into a structure similar to ACL with respect to the different mechanical stresses the ligament has to sustain.

A retrospective study of the midterm outcome of two-bundle anterior cruciate ligament reconstruction using quadrupled semitendinosus tendon in comparison with one-bundle reconstruction

PURPOSE

The objective of the study was to retrospectively compare the outcome of the first series of a 2-bundle anterior cruciate ligament reconstruction technique using quadrupled semitendinosus tendon with that of a 1-bundle reconstruction technique from 1992 through 1996.

TYPE OF STUDY

Case-control study.

METHODS

The 1-bundle group consisted of 56 patients with a follow-up period of 24 months or more (average, 46.5 months). The 2-bundle group consisted of 79 patients with a follow-up period of 24 months or more (average, 40.8 months). Manual knee laxity tests, anterior stability with KT-1000 (manual maximum), and knee extension and flexion strength by Cybex were evaluated using an average and standard deviation, and data were categorized according to the International Knee Documentation Committee (IKDC) classification. The Lysholm scale and the subjective recovery scale were also evaluated.

RESULTS

A statistically greater number of patients in the 1-bundle group were positive (+ or ++) based on the Lachman test (34% in the 1-bundle group and 13% in the 2-bundle group). The average KT-1000 anterior laxity of 2.7 +/- 2.3 mm in the 1-bundle group was statistically greater than the 1.9 +/- 1.9 mm in the 2-bundle group, with a statistical power between 70% and 80%. The total Lysholm knee scale score was 93 points in both groups, and the subjective recovery score was equivalent, 82% in the 1-bundle group and 86% in the 2-bundle group, respectively.

CONCLUSIONS

There was no statistical difference based on the IKDC, Lysholm, and subjective analysis. However, there was a statistical difference in the Lachman test, anterior drawer test, and KT-1000 measurements.

LEVEL OF EVIDENCE

Level III.